What size car seat does my child need now?

Why nobody says “group 1” any more

The group numbers come from the older European standard, which sorted seats by the child’s weight into five bands:

The overlaps were deliberate — a seat could be approved for several groups at once, which is why “0+/I” and “I/II/III” seats exist and why one box could claim to cover a child from birth to twelve.

New seats use height instead

A seat made to the current standard is approved against your child’s height, so its label reads something like 40–105 cm and mentions no group at all. That is a better measure, because height is what decides whether your child’s head is still protected by the shell. Two three-year-olds who weigh the same can differ by more than ten centimetres.

Which is also why there is no official conversion table between groups and centimetres, and why any chart claiming to give you one is guessing. If your seat is an older one, its weight range is the number that governs it — and it is still perfectly legal to use, whatever you may have read. See is your old car seat still legal?

Roughly what those heights mean by age

Seats are crash-tested with dummies built to match an average child at particular ages, which gives a rough sense of where each height band sits:

Treat this as orientation, not a target. Your child is not the average child, and no row here tells you to move them up. It does explain why the old “group 1” felt so vague: 9 to 18 kg stretches from roughly the average one-year-old to the average four-year-old, which is the entire stretch in which the rear-facing decision gets made.

How to measure without guessing

• Shoes off, against a wall. Heels, bottom and shoulders touching it, head level, and mark the top of the head with something flat. Not a tape measure waved at a wriggling toddler.
• Weight without a coat, on the bathroom scales. Both numbers on the label count, and reaching either one means that seat is done.
• Read your own seat, not the group name. The range is on the orange label on the side and repeated in the manual. The group, if it has one, is only a family name.

Then check what no number covers

A child inside the printed range can still be outgrowing the seat in practice. Rear-facing, the harness slots should be at or just above the shoulders and the head should still be inside the shell; forward-facing, the shoulders should be below the top slot. The outgrown checks go through this in order.

And whatever the numbers say, moving up a stage is never something a child grows into on schedule. It is something they outgrow the previous stage out of, and later is better than earlier at every single step.

“They’re near the top of the range — should I move them up?”

Not until they have to. Every stage protects better than the one after it, so the seat your child is in now is almost certainly doing a better job than the next one will. Being close to a limit is not a reason to move — reaching it is.

Two things are worth knowing while you wait it out. Feet touching the back of the vehicle seat is not a sign of anything; children fold their legs comfortably and it does not shorten the time they can stay rear-facing. And a booster is the stage people rush most, because it looks like a promotion — but it hands the job of holding your child to the adult belt, which only works once they are big enough for it to sit across the hip bones and the collarbone rather than the stomach and the neck. The five-step readiness test is the check for that, and age is not one of the five steps.

If someone hands you a seat

“Group 1, fits from 9 kg” means it is an older seat. That is not a reason to refuse it — those approvals are still valid and there is no expiry on using one — but its label will not give you a height range, and it was approved without a side impact test. Check its history and the expiry date stamped on the shell first: what to check on a used seat.